Method for transmitting the speech by high-frequency waves



Dec. 10, 1929. 1,739,455

METHOD FOR TRANSMITTING THE SPEECH BY HIGH FREQUENCY WAVES w. E. E. HABANN Filed Sept. 17, 1924 tomkEdxEI Patented Dec. 10, 1929 UNITED STATES PATENT OFFICE WILHELH EDUARD ERICH HABANN, OI BERLIN, GERMANY METHOD FOR rnairsurrrmo rm: srnnon nxmen-rnnounncr waves Application filed September 17, 1924, Serial No. 738,297, and in Germany October 2, 1923.

In the employment .of interrupters according to the specification of United States Patent No. 1,569,481 or similar transmitters for transmitting speech by the aid of electric waves, in which the speech is resolved solely by mechanical high frequency interruption, or ohmic, or inductive, or capacityresistance changes into high frequency impulses, and thus converted into modulated high frequency currents, the difficulty is experienced that if a receiver such as the usual audion receiver, for instance, is used, there is distortion of the speech. This distortion occurs, because, while single sounds can be heard fairly distinctly in the audion receiver,

the clearness decreases when speech of a plurality of sounds is to be transmitted. This drawback, it is true, can be overcome in a known manner, if a minor continuous ourrent be added to, or compounded with, the low frequency speaking current. The use of this continuous current, however, is inconvenient in that it causes continuous, thou h weak, electric vibrations, which must it.

avoided for reliable multiplex conversation.

For a long time the causes of such speech distortion were sought in the mechanical high frequency interrupter itself, and proposals for improvement were directed to construeso tive alterations in the interrupter, until it was found, with surprise, that-the high frequency interrupter itself was not the source of the trouble. It was then found that when working, for instance, with high frequency interrupter according to the said specification Patent Number 1,569,481, together with a receiver constructed similarly to the transmitter, all difficulties were removed. It was also found that the frequency interrupter was capable of working reversibly, in that it not only converts, on the transmitter side, low frequency speech into sound-damped high frequency currents, but also converts sounddamped high-frequency currents into low ceiver analogous to one another it is merely frequency s eech. The electric connectionnecessary that both devices should have mechanical frequencies in strict harmonic relation, that is to say, the ratio of the frequencies of the interrupters shall be unity or a fraction whose denominator shall always be a whole number. It is not essential however that the frequencies of the interrupters shall be synchronousl in phase, in other words,'the mechanical breaks need not occur simultaneously.

Now by the invention it is possible to transmit speech undistorted and perfectly distinctly without the addition of, or compounding with, continuous currents on the transmitter side which would prejudice multiplex conversation, and therefore without any continuous or undamped high frequency current on either the transmitter side or the receiver side. A rectifier on the receiver side is not necessary.

In the drawing the sole figure represents diagrammaticallya system for transmitting speech by electric waves shown by way of example for carrying out the invention.

The speaking currents from the subscribers station A which includes a microphone a and a telephone b, are conducted by the transformer T on both sides of the condenser k to the circuit 0, in which by the plugs 10 and 11 is included a mechanical interrupter of any kind (not shown) for instance such as is described in applicants former Patent No. 1,569,481. By these means the speakin currents are divided up and conducted to t e oscillatory circuit S which is coupled with the long-distance line F which at its other end is con led with a similar system of another subscri ers station B. The latter may be considered the receiver if station A is used as sender.

It is indispensible that the sending oscillatory circuit S and the receiving oscillatory circuit S: are tuned to the same frequency. The frequencies of the interrupters may be either the same' 'as the frequency of the said 95 oscillator circuits or the frequency of said circuits ivided by 1, 2, 3, or any other inte er.

t is not essential that this integer be the same for the two interrupters, consequently, 100

the ratio of the interrupter frequencies may have such values as 1 2; 4: 5; 3: 2; 6 :1, etc., the ratio 1: 1 being excluded.

By the invention multiplex conversation absolutely free of interference with distinct speaking, is rendered possible, because the presence is avoided of any undamped transmitter which would cause disturbances by interferences owing to the spatial or unipolar relationship to the rest of the highly sensitive parts of the apparatus.

Havin now particularly described and ascertainetf the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is In the transmission of speech by electric waves in which low frequency speech currents are resolved into impulses by the aid of mechanical interrupters in which a similar arrangement is operative on the receiving side as on the sending side, whereby both the sending device and the receiving device are connected with the main line over electric resonance circuits, tuned to the same frequency, the method which comprises operating the sender and the corresponding receiver with mechanical transmission frequencies which are in exact harmonic relation other than a one to one relation with one another.

WILHELM EDUARD ERICH HABANN. 

